I do not have samba installed, yet I can access Windows shares.

Click on Places/Network. You should see "Windows network," double-click on it.
You should see the workgroup name, double-click on it. You should see
individual computers in the workgroup, double-click on one. You should see a
list of shares on that computer, double-click on one. You should see a list of
files. You can copy or cut files from there to a Place on your Ubuntu computer,
or paste files from your Ubuntu computer. Or double-click on a file to open it,
just as you would any local file.